1. Field of the Invention
The invention relates to the field of safety devices for marine engines for small craft.
2. Description of the Prior Art
Whereas for much of the past outboards and even inboard engines in small marine craft were notoriously noisy, newer craft are being fitted with outboard engines such as the, Mercury Vorados, which are so quiet that someone swimming up to the boat, a diver or water skier, would have no idea the motor was running and could easily swim right up to a spinning prop. Even the boat operator might be unaware whether the engine was running and in particular if the propeller was spinning at idle or low speeds. Some propeller designs are such that at low engine speed or idle, very little propulsive force, if any, is provided to the craft by the spinning propeller. It would be difficult in many cases to distinguish normal drift from very slow forward motion, or the forward motion itself could be cancelled or even overcome by an opposing current or wind.
Houseboats have long had special risks in this area. Swimmers are often near them or climbing on them, they move infrequently, poor visibility of the props from the operating station, their engines are not as loud in the water as those of smaller craft, few visual indicators to swimmers the boat is about to get underway and large, slow rotating props may be more likely to draw people into them.
Many of the prior art designs to prevent prop injury have been directed to various types of cages or mechanical means which prevent a swimming from physically contacting the prop. However, these devices tend to interfere with performance and are subject to damage and are high maintenance items with the result that they are often ultimately removed or just left off when they fall off.
Some prior art devices sense the proximity of a swimmer or object near the prop and turn the engine off or cut prop rotation when the swimmer or object enters a restricted zone. However, such proximity systems are expensive, difficult to maintain under prolonged adverse environmental conditions and often unreliable.
Other kinds of marine warning or safety devices are provided to show when an engine might be running or not, but universally fail to be able to detect when the engine is actually in gear or the prop turning.
Nagakura, “Engine Control Means for Marine Propulsion,” U.S. Pat. No. 4,917,061 (1990) shows an engine control means for marine propulsion. FIG. 2 is a block diagram of the system. It is noted that a control switch 28 provides an input signal to a control circuit 29. The control circuit 29 receives, in addition to the control signal from the control switch 28, a signal from an engine running sensor 31 that indicates to the control circuit 29 whether the engine is running or not. The control circuit 29, in turn, outputs control signals to the starter 18 for starting or to a kill circuit 32 for stopping of the engine 13. If desired, the control circuit 29 may also operate a display 33 which will indicate whether the engine is running or not. Nagakura's display 33 does not indicate if the engine is in gear or not when it is running, but is used only to protect the starter from being used after the engine is running.
Dyches, “Starting Apparatus For Internal Combustion Engines,” U.S. Pat. No. 5,601,058 (1997) shows an apparatus for starting an engine that has an electric DC starter motor. As seen in FIG. 5, the output signal can be used by the device to de-energize the starter motor and to drive a display indicating whether the engine has started or not. In the preferred embodiment, a light or audible alarm may be employed. Again Dyches is concerned with turning a starter off once the engine is started and has nothing to do with whether the engine is in gear.
Jones, “Motor Control Circuit,” U.S. Pat. No. 4,121,140 (1978) shows a motor control circuit for preventing automatic restarting of an electric motor following an interruption of electric current flow. The invention contains auxiliary components schematically indicated as 32 in FIG. 2 which normally operate simultaneously with the motor 21, such as a light, and can be used for such purposes as a light delay relay, an electrically operated brake, or a motor running indicator, etc. Jones is concerned with preventing undesired restart of an electric motor and has nothing to do with whether the engine is in gear.
Burkenpass, “Portable Helm,” U.S. Pat. No. 4,739,236 (1988) describes a hand-held controller which can be plugged into multi-pin connector sockets wired at various parts of the ship. It is designed to be lightweight and compact and has a hook or hanger to facilitate stowing onto a bulkhead, and a hand grip to conveniently carry it in one hand. Idle indicator lamps are provided on the controller to verify the engine's idle status. The system can operate alone or an adjunct to existing helm systems. While idle status is indicated, Burkenpass fails to disclose whether the engine is in gear.
Suganuma, “Electrical System For Marine Outboard Drive,” U.S. Pat. No. 6,446,593 (2002) shows in FIG. 6, an indicator 384 can be provided in this system and can be coupled with the ECD 214 through an indication signal line 386. The indicator 384 can indicate abnormal conditions in the power supply and additionally can indicate other data, such as various engine running conditions. There is no teaching relating to whether the engine is in gear.
What is needed is some type of warning device that overcomes each of the limitations of the prior art.